Critical Point

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Entry by Andrew Capulli

Definition: Critical Point

The Critical Point indicates the Chi value that separates the situation where mixtures are always stable and the situations where mixtures are unstable or metastable where the resultant mixtures then separate into components (eventually if metastable and instantly is unstable). The "resultant mixtures" of a metastable separation are the concentrated

Example Discussion of the Critical Point

For AP225 students, this discussion is based on the diagrams used in the course notes

The critical point is where the spinodal line and the coexist curve are equal (Spinodal1.jpg as defined in the Jones text used in Soft Matter AP225). The critical point is where the either a stable or unstable solution can occur (Chi=2 in figures below). At the critical point the free energy of the system is a straight line with no minima; at any Chi less than 2, no contribution is given to the production of the diagram on the left (below)



The Science of Chocolate: interactive activities on phase transitions, emulsification, and nucleation